Endogenous molecules (substances) that form radical intermediates, i.e., having free radicals, such as ubiquinone (CoQ), vitamin K, ascorbic acid, or flavin adenine dinucleotide (FAD) and like, play an important role in the maintenance of constancy in vivo (homeostasis). In particular, being one of the electron carriers present in the inner membrane of the mitochondria that all cells have and/or in the cell membrane of prokaryotes, ubiquinone is deeply involved in the retention of mitochondrial function. For this reason, ubiquinone is expected to improve the intracellular mitochondrial function and to exhibit antioxidant and anti-aldosterone effects, and is also used as an adjuvant for cardiac function and the like.
Ubiquinone is a molecule involved in the transfer of electrons, called the Q cycle in mitochondrial respiratory chains I to III, and mediates electrons between the respiratory chain complexes I and III in the electron transfer system, thereby generating a semiquinone free radical in the process of a metabolism thereof. Free radicals such as this are related to an in vivo redox reaction. In vivo redox reaction is a concept which encompasses, in totality, the expression of a physiological functions mediated by an oxidation reduction reaction along with the production of active species thereof and the metabolism-reaction of the produced active species with biomolecules, which reaction has been suggested to be closely involved with a number of physiological phenomena and/or in vivo redox diseases that include cancer and diabetes.
Therefore, it is proposed that if there were a method available to directly visualize the behavior and modalities of the oxidation and/or reduction reaction of endogenous biomolecules such as ubiquinone, that would enable, from information on such endogenous molecules, in a variety of diseases, the elucidation of disease mechanisms, and diagnoses/treatments.
Conventional methods for in vivo imaging, such as this, include X-ray CT, PET, CT, magnetic resonance (MRI) and the like which have been conducted primarily for morphology imaging to perform spatial information imaging, but recently, in addition to morphology, functional imagining has come to be practiced which visualizes in vivo functions and phenomena.
For example, there is a case where a measurement is made by an electron spin resonance method, and the like, of free radicals generated in solution prepared from an isolated organ whereby a functional analysis is made from the changes in spectral waveform and its intensity, While that method allowed an in vitro level analysis, it has failed to show when, where, and how a substance in the body is associated with a given disease.
In addition, there is known a method for detecting-analyzing an in vivo oxidation reduction reaction that calls for administering to the body a synthetic nitroxyl radical compound as a probe, thereby using the compound's oxidation-reduction reaction as an indicator for the detection and analysis thereof However, that method which allows detection-analysis of the oxidation-reduction reaction in vivo, with the reaction of the synthetic nitroxyl radical compound as the indicator, has never been meant to directly detect and analyze the oxidation-reduction reaction of biomolecules.